The invention relates to a method of controlling the timing of the firing of printhead nozzles and to a printhead chip and printer operating according to the method.
Various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending United States patent applications filed by the applicant or assignee of the present invention on May 23, 2000: NPA001US, NPA002US, NPA003US, NPA004US, NPA005US, NPA006US, NPA007US, NPA008US, NPA009US, NPA010US, NPA012US, NPA016US, NPA017US, NPA018US, NPA019US, NPA020US, NPA021US, NPA030US, NPA035US, NPA048US, NPA050US, NPA051US, NPA052US, NPA075US, NPB001US, NPB002US, NPK002US, NPK003US, NPK004US, NPK005US, NPK007US, NPM001US, NPM002US, NPM003US, NPM004US, NPN001US, NPN002US, NPN003US, NPP001US, NPP002US, NPP003US, NPP005US, NPP006US, NPP007US, NPP008US, NPP016US, NPP017US, NPP018US, NPP019US, NPS001US, NPS003US, NPS020US, NPT001US, NPT002US, NPT003US, NPT004US, NPX001US, NPX003US, NPX008US, NPX011US, NPX014US, NPX016US, NPX020US, NPX022US, IJ52US, IJM52US, MJ10US, MJ11US, MJ12US, MJ13US, MJ14US, MJ15US, MJ34US, MJ47US, MJ52US, MJ58US, MJ62US, MJ63US, PAK04US, PAK05US, PAK06US, PAK07US, PAK08US, PEC01US, PEC02US, PEC03US.
In addition, various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending United States patent applications filed simultaneously by the applicant or assignee of the present invention: PEC04US, PEC06US, PEC07US.
The disclosures of these co-pending applications are incorporated herein by cross-reference. Each application is temporarily identified by its docket number. This will be replaced by the corresponding USSN when available.
Of particular note are co-pending U.S. patent applications MJ62US, IJ52US, IJM52US, MJ63US, MJ58US, which describe a microelectomechanical drop on demand printhead hereafter referred to as a Memjet printhead.
The above Memjet printhead is a multi-segment printhead that is developed from printhead segments that are capable of producing, for example, 1600 dpi bi-level dots of liquid ink across the full width of a page. Dots are easily produced in isolation, allowing dispersed-dot dithering to be exploited to its fullest. Color planes might be printed in perfect registration, allowing ideal dot-on-dot printing. The printhead enables high-speed printing using microelectromechanical ink drop technology.
Co-pending U.S. patent applications PEC01US, PEC02US, PEC03US, PEC04US, PEC06US, and PEC07US describe a print engine/controller suited to driving the above referenced page wide multi-segment printhead.
A multi-segment printhead of the above kind may field 1280 nozzles. Firing all the nozzles together would consume too much power. It could give rise to problems in terms of ink refill and nozzle interference.
Firing logic controls the firing of nozzles. Normally the timing of firing of nozzles in a printhead is controlled externally. It is desirable to reduce the complexity that arises in external printhead controllers as a consequence of this. Further, at the printhead, each of the colored inks used has different characteristics in terms of viscosity, heat profile etc. Firing pulses should therefore be generated independently for each color.
The invention resides in control of the firing of nozzles in a printhead, the nozzles being on rows for respective ink channels in the printhead. Print data is loaded to respective channel shift registers for respective channels. All the print data is transferred to nozzle enable bits provided one per nozzle and the nozzles in respective channels are fired in time independent manner using separate timing generators in each channel.
Moving the timing mechanisms onto the printhead helps reduce complexity. In addition, as each color channel is given its own timer, a given color""s firing pattern can be started at any time. It need not be an exact number of dot-lines from another. It is possible to print dot on dot via appropriate staggering of the start timing in respective channels although this regime is not adopted in the preferred embodiment described below.
Normally the widths and profiles of firing pulses are generated externally to the printhead. In the preferred embodiment below the pulse widths of electrical pulses by which to fire the nozzles is programmable.
With the above in mind, the nozzles are fired by an electrical pulse. The profile of the pulse is programmed to suit the ink at the nozzle. Ideally the printhead includes ink nozzles in multiple rows, successive rows of nozzles defining respective ink channels and an electrical pulse train fires the nozzles. Pulse profiles in the pulse train are programmed to suit the ink in respective channels. Ideally, programmed bits loaded to a timing generator adjust the pulse profile. Ideally the programmed bits exist in tables loaded to the printhead, one for each channel, the tables being programmed via the printhead serial interface. The nozzle rows are preferably in offset pairs for each channel and firing of the offset pairs is effected by out of phase pulse trains.
With the above multi-segment printhead (Memjet) technology (outlined in the referred-to documents) the microelectromechanical process is added to a CMOS process by which to construct the printheads. The consequent printhead is a new type. The marriage with CMOS technology allows inclusion of logic in the printhead chip. It is an ideal place to locate timing circuitry for firing of nozzles.
In a particular form the invention resides in a method of controlling a printhead including nozzle rows, successive rows of nozzles defining respective ink channels wherein the nozzles in respective channels are similarly grouped and groups are fired successively. Ideally respective rows of nozzles are organized in repeated pods of nozzles along the length of each row of nozzles, the nozzles in a pod being fired one after the other along the row; successive pods of respective channels are linked as a chromapod wherein the one after the other firing of nozzles in each channel is in step along the row of nozzles in the respective pods; and blocks of chromapods are operated as a firegroup, the firegroups firing together. The nozzles within a single segment are grouped physically to reduce ink supply complexity and wiring complexity. They are also grouped logically to minimize power consumption and to enable a variety of printing speeds, thereby allowing speed/power consumption trade-offs to be made in different product configurations.